Leaf through the pages of any newspaper or magazine, and human genetics is seldom far from the front page or cover. From disputes over the accuracy of blood tests in the O.J. Simpson trial to discoveries of the latest disease-related gene and the promise held out for gene therapies, molecular biology is big news, and, increasingly, big business.

Yet seldom do readers get any view, let alone a clear one, into how these developments come about. Nor does daily coverage uncover the clashing egos and agendas that can fuel the competition to develop the genetic ''magic bullets'' that researchers hope to incorporate into a person's genetic makeup, which they hope will cure -- perhaps for all time -- some of the most insidious diseases facing humanity. Such views might be less important in another subject area. But gene therapies involve changing the molecules inside the body that form the unique genetic blueprint for every human being. It pays to know who is revising the drawings.

''Altered Fates: Gene Therapy and the Retooling of Human Life'' is an engrossing, thought-provoking remedy to these shortcomings. The book is laden, though not leaden, with richly descriptive detail: ''Inside, countless billions of microbial lab assistants, E. coli bacteria, grow up cozily and happily with new genes spliced in, forming colonies, making foreign proteins, and dividing like mad in gamy little dishes of agar jelly that smell like a high school boy's gym locker.'' As if to drill into readers the horror of certain diseases, the authors also provide occasional graphic descriptions of symptoms -- not entirely necessary for the story.

But the authors also display a sense of pacing that prevents such detail from turning into a morass that might send a reader packing.

The book divides roughly into two parts: the first dealing with the people and events that led to the first experiments in altering a human's genes for therapeutic reasons; the second, a broader look at the biomedical field and the economic and ethical issues raised by genetic engineering in humans.

In many ways, the first part makes the most compelling reading because it offers a rare verbal diorama of the struggle between two eminent scientists over the first gene-therapy experiments.

William French Anderson, a brilliant, driven biochemist at the National Institutes of Health (NIH), led the four-member team that conducted the first experiments. One is never clear how much of his effort is driven by concern for his patients and how much by ambition to make his mark in the field -- even as he is hailed by the families of volunteers who take part in his experiments.

On the other side is Richard Mulligan, a biologist at MIT's Whitehead Institute in Cambridge, Mass., who also sees promise in genetic therapies. He challenges the quality and rigor of the research that lay behind Dr. Anderson's efforts to begin gene-therapy experiments on humans.

In the meetings leading up to NIH approval of Anderson's experiments (which in turn led to a flood of subsequent approvals), it was a contest between clinicians, who daily face patients they can no longer help, and scientists, who demanded fewer uncertainties than Anderson's proposals could deliver. Dr. Mulligan says: ''What [Anderson] has done is gain acceptance by the public of the idea of gene therapy. That's positive.... But he has not spawned any good experiments. We still don't know if gene therapy is really safe or not. We're still not a step ahead clinically. The science so far has been abysmal.''

Sour grapes or useful warning? Perhaps both. Meanwhile, research proceeds along several fronts, as do the growing commercial and political interests in exploiting the fruits of that research -- as the authors describe in later chapters. They end with their own warning: ''...Most nightmarish scenarios ignore the innate good sense of people; common sense and an instinct for fair play, backed by the power of federal laws, it is assumed, will enable us to do good and protect us from doing ill. Nevertheless, the body politic still works its will through its representatives in government and the judiciary. These representatives in turn are influenced by powerful forces in the professions, business, and academe. The rather inglorious way that the scientific and administrative elite are handling the earliest fruits of gene therapy is ominous.''

A second Pulitzer on this subject may be in order for this Chicago Tribune writing team, following one for journalism in 1987.